}

  @Test
  fun synchronousCallAccessors() {
    val ready = CountDownLatch(2)
    val waiting = CountDownLatch(1)
    client =
      client.newBuilder()
        .addInterceptor(
          Interceptor { chain: Interceptor.Chain? ->
            try {
              ready.countDown()
              waiting.await()
            } catch (e: InterruptedException) {
              throw AssertionError()
            }

   * found in any textbook.
   */

  /** Monitor guarding all access */
  final Monitor monitor;

  /** Guard for waiting takes */
  private final Monitor.Guard notEmpty;

  /** Guard for waiting puts */
  private final Monitor.Guard notFull;

  // Internal helper methods

  /** Circularly increment i. */
  final int inc(int i) {

   * throttled threads will <b>not</b> be awakened as a result of this invocation, thus they do not
   * observe the new rate; only subsequent requests will.
   *
   * <p>Note though that, since each request repays (by waiting, if necessary) the cost of the
   * <i>previous</i> request, this means that the very next request after an invocation to {@code
   * setRate} will not be affected by the new rate; it will pay the cost of the previous request,

sang this, very slowly and sadly:--


`"Will you walk a little faster?" said a whiting to a snail.
"There's a porpoise close behind us, and he's treading on my
 tail.
See how eagerly the lobsters and the turtles all advance!
They are waiting on the shingle--will you come and join the
dance?

Will you, won't you, will you, won't you, will you join the
dance?

    private final Executor adapterExecutor;

    // The execution list to hold our listeners.
    private final ExecutionList executionList = new ExecutionList();

    // This allows us to only start up a thread waiting on the delegate future when the first
    // listener is added.
    private final AtomicBoolean hasListeners = new AtomicBoolean(false);

    // The delegate future.
    private final Future<V> delegate;

This can be reading from Kubernetes and writing other objects back, writing to proxies over XDS, etc.

Unfortunately, writing controllers is very error prone, even for seemingly simple cases.
To work around this, Istio has a variety of abstractions meant to make writing controllers easier.

## Clients

    latch = new CountDownLatch(1);
    future = createListenableFuture(Boolean.TRUE, null, latch);
  }

  @Override
  protected void tearDown() throws Exception {

    // Make sure we have no waiting threads.
    latch.countDown();
  }

  /** Constructs a listenable future with a value available after the latch has counted down. */
  protected abstract <V> ListenableFuture<V> createListenableFuture(

    TimeoutException e =
        assertThrows(
            TimeoutException.class, () -> service.startAsync().awaitRunning(1, MILLISECONDS));
    assertThat(e)
        .hasMessageThat()
        .isEqualTo("Timed out waiting for Foo [STARTING] to reach the RUNNING state.");
  }

  private static class TestService extends AbstractIdleService {
    int startUpCalled = 0;
    int shutDownCalled = 0;

<font color="#4E9A06">INFO</font>:     Waiting for application startup.
<font color="#4E9A06">INFO</font>:     Application startup complete.
<font color="#4E9A06">INFO</font>:     Started server process [<font color="#06989A">27369</font>]
<font color="#4E9A06">INFO</font>:     Waiting for application startup.
<font color="#4E9A06">INFO</font>:     Application startup complete.

   * @param numElements the number of elements to be waited for
   * @param timeout how long to wait before giving up
   * @return the number of elements transferred
   * @throws InterruptedException if interrupted while waiting
   * @since 28.0 (but only since 33.4.0 in the Android flavor)
   */
  @CanIgnoreReturnValue
  @J2ktIncompatible
  @GwtIncompatible // BlockingQueue
  public static <E> int drain(